Dry free flowing peroxygen composition with an organic acid anhydride and alkali metal hydrate

ABSTRACT

A DRY, STABLE NON-SEGREGATING BLEACHING COMPOSITION HAVING A CONTROLLABLE, MODERATELY LOW BULK DENSITY WHICH COMPRISES A MASS OF EXPANDED, POROUS, WATER-SOLUBLE INORGANIC HYDRATE SALT PARTICLES HAVING AT LEAST ONE PEROXYGEN COMPOUND BONDED THERETO. THE PEROXYGEN COMPOUND IS BONDED TO THE EXPANDED, POROUS SALT PARTICLES AT MODERATELY LOW TEMPERATURES UNDER CONTROLLED MOISTURE CONDITIONS.

"United States Patent O1 fice 3,64%,885 Patented Feb. 8, 1972 3,640,885 DRY, FREE FLOWING PEROXYGEN COMPOSITION WITH AN ORGANIC ACID ANHYDRIDE AND ALKALI METAL HYDRATE Raymond C. Rhees, Whittier, Califl, assignor to Ken McGee Chemical Corporation No Drawing. Filed Sept. 24, 1968, Ser. No. 762,151 Int. Cl. C01b /00 US. Cl. 252186 34 Claims ABSTRACT OF THE DISCLOSURE A dry, stable non-segregating bleaching composition having a controllable, moderately low bulk density which comprises a mass of expanded, porous, water-soluble inorganic hydrate salt particles having at least one peroxygen compound bonded thereto. The peroxygen compound is bonded to the expanded, porous salt particles at moderately low temperatures under controlled moisture conditions.

The stability of the peroxygen compound may be further increased by bonding at least one peroxygen decomposition inhibitor to the expanded, porous salt particles.

An active and effective oxidizing and bleaching composition is also provided which comprises a mixture of a first quantity of expanded, porous particles having at least one water soluble peroxygen compound bonded thereto and a second quantity of said expanded porous particles having bonded thereto at least one organic acid anhydride. A peroxygen decomposition inhibitor may also be included in this composition.

A bleaching composition which is not only stable, nonsegregating and has a controllable, moderately low bulk density but is also eifective at mild temperatures is also provided by the present invention. Such a composition comprises a mass of the expanded, porous particles having at least one peroxygen compound, at least one watersoluble alkali metal silicate and at least one acid anhydride bonded to the expanded, porous particles. The peroxygen compound and the alkali metal silicate are bonded to one quantity of particles and the acid anhydride is bonded to a separate quantity of particles, after which the two quantities are intimately mixed to provide a substantially uniform bleaching composition.

BACKGROUND OF THE INVENTION (1) Field of the invention This invention relates to novel bleaching compositions and to methods of preparing such bleaching compositions. More particularly, the invention relates to dry, free-flowing bleaching compositions containing an inorganic peroxygen compound, the compositions having good shelf stability and a controllable, moderately low bulk density.

(2) Description of the prior art It is well known that inorganic peroxygen compounds, such as alkali metal and alkaline earth metal perborates, percarbonates, persulfates, perphosphates and the like, are effective bleaches. The bleaching action of such inorganic peroxygen compounds results from the release of active" oxygen which occurs in the presence of water. This release of oxygen is a function of temperature and increases rapidly at temperatures above about 60 C. These peroxygen compounds are known to have a gentle bleaching action on textile fibers of all kinds, including colored and synthetic fibers, and are particularly useful as a bleaching agent in detergent compositions intended for household use.

Despite their known advantages, such peroxygen compounds suffer from a number of disadvantages which make their use in bleaching, detergent and like compositions less than completely satisfactory. Thus, peroxygen compounds decompose relatively rapidly in the presence of moisture such as when stored in an open package in a humid atmosphere. This rate of decomposition of the peroxygen compounds may also be increased when any of a large number of commonly used accelerators are present in the package with the bleaching composition.

In addition, while it is generally preferred that bleaching, detergent and like compositions intended for household use have a bulk density of about 15 to 30 pounds per square foot, peroxygen compounds, as provided commercially, usually have a substantially higher bulk density. The relatively low bulk density requirement for home laundry products is not met merely by physically blending the peroxygen compound with commonly used low density builders or fillers because the high density peroxygen compound tends to separate out and accumulate at the bottom of the package.

Furthermore, while peroxygen compounds are increasingly effective as bleaches as the boiling point of water is approached, their bleaching effectiveness is markedly reduced at relatively mild temperatures, that is, about 50 C. and below. This poor bleaching activity at mild temperature has limited the acceptance of peroxygen bleaches in those areas where home laundry is generally done at relatively mild temperatures within a short period of time. While a number of activators have been proposed to permit the bleaching operation to be carried out at such mild temperatures, the use of these activators has given rise to other problems. For example, the activator used must be mixed with the peroxygen compound in such a manner that decomposition of the peroxygen compound does not occur during formulation, packaging, shipping and storage and so that the ingredients can simply be added to the laundry Water as a uniform composi tion. Heretofore, in order to achieve these objectives, it has usually been necessary to provide layered compacts or separate packages of the bleaching component and the activator to prevent interaction and segregation of the ingredients. However, these approaches increase packaging costs prohibitively and decrease convenience in use.

It has recently been discovered that the oxidation potential of a peroxygen compound in an aqueous liquid may be markedly increased by incorporating a alkali metal silicate and an organic acid anhydride with said peroxygen compound in the aqueous liquid. That discovery is disclosed and claimed in copending application Ser. No. 761,708, filed concurrently herewith, by Faye J. Donaghu, entitled Method and Composition and assigned to the same as the present invention.

SUMMARY OF THE INVENTION The present invention provides various compositions including one or more peroxygen compounds, alkaline silicates and organic acid anhydrides in novel formulations which are dry, stable, free-flowing, non-segregating and have controllable, moderately low bulk densities.

Thus, a dry, stable, non-segregating peroxygen bleaching composition having a controllable, moderately low bulk density may be provided by bonding at least one peroxygen compound to particles of an expanded, porous, water-soluble inorganic hydrate salt carrier. The bonding of the peroxygen compound to particles of the expanded, porous carrier is effected at moderately low temperatures under relatively dry conditions to thereby substantially eliminate descomposition of the peroxygen compound.

The stability of the peroxygen compound may be further increased by bonding at least one peroxygen decom position inhibitor to the expanded, porous carrier.

In accordance with another aspect of this invention, a peroxygen bleaching composition is provided which not only is stable, non-segregating and of controllable, moderately low bulk density but which is also efiective as a bleach at mild temperatures. This bleaching composition comprises a mass of the expanded, porous, water-soluble morganic hydrate salt particles having bonded thereto at least one Water-soluble peroxygen compound which is capable of forming hydrogen peroxide in an aqueous medium, at least one water-soluble alkali metal silicate and at least one organic acid anhydride which is capable of reacting with the peroxygen compound in an aqueous medium to form a peroxy acid. To prevent premature reaction between the constituents of the composition in the presence of free water during preparation, handling, storage and the like of the composition, the peroxygen compound and the silicate are bonded to the one quantity of the expanded, porous particles, and the acid anhydride is bonded to a different group of like particles. The two groups of particles are intimately mixed to provide a substantially uniform bleaching composition.

The use of the expanded, porous water-soluble inorganic hydrate salt particles as a carrier in the bleaching compositions of this invention enables the bulk density of the composition to be readily controlled within a desired range and contributes to the stability of the composition. Thus, the bulk density of the bleaching composition may be controlled within a desired range by controlling the bulk density of the expanded, porous particles to which the active bleaching constituents are bonded. Since the active bleaching constituents of the composition are bonded to the expanded porous carrier, segregation of these constituents in the composition is substantially eliminated. The bleaching composition may, if desired, be admixed with detergents to provide a Washing composition having bleaching properties.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A dry, free-flowing, non-segregating peroxygen bleaching composition having good shelf stability and a controllable, moderately low bulk density is provided by the present invention by bonding at least one peroxygen compound to expanded, porous, water-soluble inorganic hydrate salt particles. The expanded porous salt particles serve as a carrier for the peroxygen compound and are used as a bulking agent to control the bulk density of the bleach composition. The expanded, porous particles may also contribute other desirable properties to the bleach composition.

In accordance with one embodiment of the invention, the bleach composition comprises a mass of the expanded, porous particles having the peroxygen compound bonded thereto. Such expanded, porous carrier particles may be produced in various ways. One particularly preferred method being that disclosed in copending application Ser. No. 387,137, filed Aug. 3, 1964, now Pat. No. 3,454,357 by Raymond C. Rhees and Howard N. Hammer, entitled Process and Apparatus. As explained in that copending application, expanded porous particles are prepared by introducing a stream of an at least partially-hydrated inorganic salt, in particulate form, into an expansion Zone while separately and continuously supplying to said zone a quantity of gas having a temperature sulficient to cause said salt particles to puff, expand, intumesce, or the like. While other methods of producing the expanded, porous salt particles may, of course, be used, it is essential that the puifing process be carried out in a manner such that the hydrated inorganic salt particles are heated rapidly to a temperature above that at which the salt particles lose at least part of their water of hydration. Such rapid heating is required to produce a satisfactory pulfed or expanded product.

A variety of hydrated inorganic salts, suitable for use as the carrier in the bleaching composition of this invention, may be expanded in this manner. Such suitable inorganic hydrate salts include, for example Potassium tetraborate pentahydrate--K B O 5H O Potassium tetraborate tetrahydrateK B O 4H O Sodium metaborate tetrahydrate-Na B O 4H O Sodium metaborate octahydrateNa B O 8H O Sodium carbonate heptahydrate--Na CO -7H O Sodium carbonate monohydrateNa CO -H O Sodium sulfate heptahydrate--Na SO 7H O Sodium sulfate decahydrateNa SO -10H O Tetrasodium pyrophosphate decahydrate Na P O 10H O Soduim tetraborate decahydrate -Na B O lOH O Sodium tetraborate pentahydrate-Na B O -5H O The bulk density of the expanded, porous particles produced from these materials may be controlled within the range of from about 10 to 40 lbs/cu. ft., and preferably between about to lbs./ cu. ft. Particularly satisfactory results are obtained when a hydrated sodium tetraborate is used as the water-soluble inorganic salt. This material is generally preferred for use as the source of the carrier in the present invention, for it may be expanded under controlled conditions to provide a material of controlled water content and controlled bulk density within the desired 15 to 30 lbs./ cu. ft. range. Such expanded sodium tetraborate particles are substantially instantaneously soluble in water and have good resistance to physical breakdown despite its low density. Also, the use of expanded sodium tetraborate as the source of the carrier particles for the peroxygen compound has the additional advantage of providing the bleaching composition with the cleansing and sanitizing properties of borax. It will be understood, however, that the present invention is not limited to the use of sodium tetraborates as the source of the expanded, porous particles, for other expanded, porous inorganic salts may also be used in this invention.

Peroxygen compounds which are available in solid form may be used in the present invention. The peroxygen compound preferably used is sodium perborate and more particularly sodium perborate tetrahydrate. This material is generally preferred due to its low cost, ready availability, and good storage ability, and is available in crystalline or powder form. Other solid peroxygen compounds may also be used either singly or in combination such as other alkali metal and alkaline earth metal perborates, alkali metal and alkaline earth metal peroxides, percarbonates, persulfates, perphosphates and the like. These peroxygen compounds may be either anhydrous or in the hydrated state. Preferably hydrated peroxygen compounds are used.

The amount of peroxygen compound incorporated in bleaching composition can vary within wide limits, from the smallest amount required for effective bleaching up to about 60% by weight or more. The upper limit of peroxygen concentration in the bleaching composition is usually dependent on the desired bulk density of the composition and the concentration of other additives in the composition. Generally the composition contains between about 10% and 60% by weight of the peroxygen compound, with amounts between about and by weight being preferred.

The solid peroxygen compound is bonded to the expanded porous salt particles by intimately mixing the two materials at moderately low temperatures under relatively dry conditions. The term relatively dry as used herein refers to bonding conditions under which at no time during mixing of the materials does the total water content in the mixture (that is, free water plus that combined as water of hydration) exceed the amount which can be completely bound as the highest hydrates of the compounds present in the mixture. For example, in preparing compositions containing sodium tetraborate as the expanded, porous carrier and sodium perborate as the peroxygen compound, the amount of Water present during formulation of the composition should at no time exceed the total of that found in the hydrates and NaBO -4H O. While fully hydrated components may be used, those with lesser amounts of water of hydration are preferred. However, some free water or water which can exchange between compounds must be present during formulation to bond the components together. Thus, the bonding is carried out under relatively dry conditions.

The amount of water present in the mixture during formulation may be controlled in several ways. Thus, the solid peroxygen compound and the expanded, porous carrier particles may be admixed and moisture added to the mixture, with agitation, at a controlled rate. The free water thus added to the admixture is rapidly taken up by the porous particles and thereby bonds the peroxygen compound to the expanded porous carrier particles. The moisture may be added in any suitable manner such as spraying, atomizing, and the like.

Preferably, the amount of water present in the mixture is controlled by employing a higher hydrate of either the peroxygen compound or the expanded, porous carrier and then, in absence of added Water, mixing and heating the two components up to that temperature (transition temperature) at which one of the components releases at least a portion of its water of hydration. It has been found that the released water of hydration redistributes among the constituents of the mixture and is rapidly taken up by the porous carrier particles, thereby effectively bonding the constituents in the mixture together. It is normally expected that when a solid watersoluble hydrated peroxygen compound is heated above its transition temperature and starts to melt into the released water of hydration, decomposition of the peroxygen compound will be initiated. However, it has been discovered that when this heating is performed in the presence of the expanded, porous carrier particles substantially no decomposition of the peroxygen compound occurs. It is believed that this is due to the small amount of free water present in the mixture resulting from the rapid transfer of released Water of hydration to the expanded, porous carrier. To facilitate this transfer of released water, it is generally preferred to use a higher hydrate of the peroxygen compound and a lower hydrate of the expanded inorganic salt. In addition, it is necessary to agitate the mixture during heating to provide a substantially uniform composition.

The temperature to which the mixture is heated will, of course, depend on the components of the mixture and the degree of hydration of these components. As noted above, the mixture must be heated to at least the temperature at which one of the hydrates in the mixture releases at least a portion of its water of hydration.

According to a preferred embodiment of the invention, sodium tetraborate pentahydrate is rapidly heated to a temperature between about 400 and 500 C. to form expanded, porous particles containing between 2 and 4 moles of water per mole of tetraborate and having a bulk density of between and lbs./cu. ft. If desired, the expanded porous sodium tetraborate may then be dried to reduce the water of hydration content even further, that is to about 1 mole of water per mole of tetraborate. The use of such dried carrier particles is generally preferred for the dried carrier particles readily absorb water present in the mixture during preparation of the composition, thereby facilitating production of the composition. In addition, the dried particles absorb any free water which may 'be encountered during handling and storage of the composition, thereby preventing decomposition of the peroxygen compound prior to use.

The dried tetraborate particles are placed in a container and mixed with finely divided sodium perborate tetrahydrate (NaBO -4H O). The mixture is then heated to about 5570 C. with continued agitation. In this temperature range, the sodium perborate releases some of its water of hydration, with the released water being transferred to the sodium tetraborate. This transfer of water from the hydrated perborate to the expanded tetraborate particles not only bonds the components together, thereby preventing segregation during handling and storage, but also provides a composition having increased stability, for the lower hydrates of sodium perborate are more stable than the tetrahydrate. The resulting product is dry, uniform and free-flowing. Since the perborate is bonded to the expanded tetraborate particles, segregation of these materials does not occur upon handling and storage.

If desired, the stability of the bleaching composition may be further increased by including at least one peroxygen decomposition inhibitor in the composition. The decomposition inhibitor may be either physically mixed with the bonded peroxygen compound-expanded carrier product to provide a uniform composition or it may also be bonded to the expanded porous particles together with the peroxygen compound. While a physical mixture of the decomposition inhibitor is effective in preventing decomposition of the peroxygen compound, such a composition is generally not preferred since the decomposition inhibitor is not thereby bonded to the expanded carrier particles.

Suitable decomposition inhibitors which may be used either singly or in combination include, for example, alkali metal silicates such as sodium metasilicate, sodium orthosilicate, sodium sesquisilicate, sodium disilicate, potassium metasilicate, potassium disilicate, and the like; alkaline earth metal silicates such as magnesium silicate, barium silicate, zinc silicate, calcium silicate and the like; conventional metal chelating agents such as ethylene tetraacetic acid and derivatives thereof and the like. Generally, it is preferred to use sodium metasilicate, either anhydrous or in a hydrated form, as a decomposition inhibitor in the bleaching composition.

Preferably, the decomposition inhibitor, together with the peroxygen compound, is bonded to the expanded porous carrier particles to thereby prevent the inhibitor from separating from the composition during handling or storage. The decomposition inhibitor may be bonded to the carrier particles at the same time as the peroxygen compound or separately therefrom. When the inhibitor and the peroxygen compound are bonded to the carrier particles at the same time, the components are intimately mixed and heated under relatively dry conditions in the manner described hereinabove. The decomposition in hibitor may, if desired, also be bonded to the expanded porous particles either prior or subsequent to bonding the peroxygen compound to the particles by admixing a hydrated decomposition inhibitor with the particles and heating the mixture under relatively dry conditions as described hereinabove. However, the decomposition inhibitor may also be bonded to the expanded, porous particles by the addition of a controlled amount of moisture to a mixture of the peroxygen compound, the inhibitor and the expanded porous particles. According to this embodiment, an aqueous solution of the decomposition inhibitor may be sprayed, atomized or otherwise applied to an admixture of the peroxygen compound and the expanded porous particles, with agitation, at room temperature, to bond the constituents together.

When a decomposition inhibitor is used, its concentration in the bleaching composition may be widely varied. Amounts between about 0.01 and 0.1 part by weight of the decomposition inhibitor per part by weight of the peroxygen compound are generally preferred. Greater amounts may be used but are generally not required. Thus, the decomposition inhibitor may comprise between about 0.1% and 6% by weight of the bleaching composition.

Other additives such as surface active agents, coloring agents, perfumes and the like may also be bonded to the expanded porous salt particles according to the procedure described hereinabove, provided they do not actively promote decomposition of the peroxygen compound or adversely react with or affect the properties of the expanded, porous salt particles. The bleaching composition may also be admixed with detergents to provide a detergent composition having bleaching properties.

The bleaching composition thus prepared provides all of the good bleaching properties of a peroxygen bleach, namely mildness to fabrics and effectiveness at high bleach temperatures. In addition, the compositions have excellent stability, shelf life and are non-segregating. Thus, since the peroxygen compound and the decomposition inhibitor, if used, are bonded to the carrier, these materials do not segregate during handling or storage. Moreover, since the density of the expanded porous carrier can be controlled to desired, predetermined values, finished compositions can now be formulated so as to have any desired bulk density. Furthermore, when it is desired to admix the bleaching composition with a detergent, the bulk density of the bleaching composition may be controlled to that of the detergent and thereby reduce the tendency of the bleaching composition from segregating from the detergent.

In accordance with another aspect of the invention, a

peroxygen bleaching composition is provided which is not only stable, non-segregating and of controllable, moderately low bulk density but which is also effective as a bleach at mild temperatures. This bleaching composition comprises a mass of the expanded, porous inorganic salt particles described hereinabove having bonded thereto at least one water-soluble peroxygen compound which is capable of forming hydrogen peroxide in an aqueous medium, at least one water-soluble alkali metal silicate and at least one organic acid anhydride capable of reacting with the peroxygen compound in an aqueous medium to form a peroxy acid. As disclosed in said copending application, Ser. No. 761,708, entitled Method and composition the peroxygen compound, the alakli metal silicate and the acid anhydride constituents combine synergistically when added to an aqueous medium to provide active oxidation species having an unexpectedly high oxidation potential even at mild temperatures. According to a preferred embodiment of the present invention, these constituents are bonded to the expanded, porous carrier particles by the process of the present invention to provide a bleach composition which is stable, non-segregating and of controllable, moderately low bulk density, but which is effective as a bleach at mild temperatures.

The peroxygen compound and the alkali metal silicate are bonded to one quantity of particles of the expanded porous salt and the organic acid anhydride is bonded to a separate quantity of the carrier particles, after which the two quantities are intimately mixed to provide a substantially uniform bleaching composition. Since the peroxygen compound and the alkali metal silicate are bonded to a separate quantity of particles than that to which the acid anhydride is bonded, premature reaction between the peroxygen compound and the anhydride, which may occur should there be any free water present during handling and storage of the composition, is prevented. Thus, both quantities of expanded, porous particles in the composition are able to absorb a considerable amount of atmospheric moisture, and bind it tightly as water of hydration, before free Water is present to promote undesired changes in the activity of the bleach.

If desired, the silicate constituent of the composition may also be bonded to a separate quantity of particles of the expanded porous carrier and then blended with other quantities of the carriers to which the other constituents have been bonded. However, in its preferred form, the

silicate is bonded to the particles containing the peroxygen compound in the manner described hereinabove.

Thus, according to this preferred embodiment of the invention, the bleaching composition comprises a substantially uniform physical mixture of two components. The first component comprises a mass of expanded, porous inorganic salt particles having at least one peroxygeri compound and at least one water-soluble silicate compound bonded thereto. The second component comprises a comparable mass of the same expanded, porous particles to which at least one organic acid anhydride has been bonded. Since the peroxygen, silicate and acid anhydride constituents are bonded to the expanded, porous particles, separation of these constiuens from he bleaching composition is substantially eliminated. Furthermore, since the bulk density of both components of the composition is subsantially the same, the mixture of the two components of the composition does not tend to segregate during shipping, handling, storage or the like. While the peroxygen and the acid anhydride constituents are effectively separated in the dry mixture whereby they will not interact, complete and rapid solution of the composition occurs on addition of the mixture to an aqueous medium whereby to rapidly form bleach active species having a high oxidation potential even at mild temperatures.

The first component of the bleaching composition of this embodiment of the invention, which comprises the peroxygen and the silicate constituent bonded to the expanded porous carrier particles, may be prepared by the procedure described hereinabove for bonding these constituents, namely by intimately mixing the materials at moderately low temperatures under relatively dry conditions. Thus, the constituents may be admixed and moisture added to the mixture, with agitation, at a controlled rate to thereby bond the materials together. Preferably, this component of the composition is prepared by admixing the expanded porous carrier particles, the peroxygen compound and the silicate constituent, at least one of which is present in a higher hydrate form, and heating the mixture with agitation to at least the transition temperature at which one hydrate in the mixture releases Water of hydration. In this manner, the water of hydration released in the mixture upon heating is redistributed among the constituents of the mixture to effectively bond them together.

The expanded porous inorganic salt particles which may be used as the carrier in this embodiment of the invention are the same as those described hereinabove.

However, not all peroxygen compounds may be used in this two-component composition of this embodiment of the invention. Peroxygen compounds which may be used are those which are available in solid form and are capable of forming hydrogen peroxide in an aqueous medium. Suitable peroxygen compounds include alkali metal and alkaline earth metal peroxides; alkali metal and alkaline earth metal perborates; salts of peroxyacids such as peroxycarbonates, peroxyphosphates and the like; and peroxyhydrates such as phosphate peroxyhydrate, sodium carbonate peroxyhydrate and the like, either singly or in combination. The peroxygen compound used must be relatively stable at room temperature so that no significant loss of active oxygen content occurs during storage. The peroxygen compound preferably used in this composition is an alkali metal perborate and more particularly sodium perborate. Both the tetrahydrate and monohydrate' form of sodium perbonate may be used since both are available commercially in crystalline or powder form and have good storage stability. Generally, the first component contains between about l()% and 60% by weight of the peroxygen compound, with amounts between about 40% and 55% being preferred.

The alkali metal silicate constituent of this component of the composition preferably is sodium metasilicate. which may be used in either its anhydrous form or in a hydrated form, such as the pentahydrate or octahydrate. Other water-soluble alkali metal silicates may also be used. For example, other water-soluble sodium silicates such as so dium orthosilicate, sodium sesquisilicate, sodium disilicate, and the like; water-soluble potassium silicates such as potassium metasilicate, potassium disilicate and the like; and other alkali metal silicates which are soluble in water may be used in the present invention, either singly or in combination.

It is believed that the silicate constituent reacts with some of the peroxygen compound in the presence of the acid anhydride, when the composition is added to an aqueous medium, to form an active oxidative species, probably a peroxysilicate. The speed with which this reaction occurs is dependent in part on the concentration of the silicate in the composition. It is generally preferred that the bleaching composition contain at least about 0.01 part by weight of the silicate constituent per part by weight of the peroxygen compound present in the composition. When at least this amount of silicate is present in the composition, the high potential oxidative species reaches its peak of oxidative potential within a relatively short period of time after addition of the composition to the aqueous medium. Lesser concentrations of the silicate may be used if longer reaction times are not undesirable. Greater concentrations of the silicate, that is, about 0.1 or more parts by weight of the silicate per part by weight of the peroxygen compound may be used. Thus, the alkali metal silicate may comprise between about 0.1% and 6% by weight of the first component of the two-component bleaching composition of this invention, with amounts between about 1% and 5% by weight being preferred.

The second component of the bleaching composition of this embodiment of the invention comprises a mass of the expanded porous carrier particles having an organic acid anhydride bonded thereto. The acid anhydrides which may be used are organic acid anhydrides which are capable of reacting with the peroxygen constituent of the composition in an aqueous medium to form a peroxy acid of the acid anhydride. The presence of a peroxy acid in an aqueous medium may be determined by the per-acid formation test described in US. Pat. No. 2,955,905, when an acid anhydride is substituted for the esters used in the test procedure described in that patent.

Suitable organic acid anhydrides which may be used, either singly or in combination, in this embodiment of the invention include, for example,

valeric anhydride phthalic anhydride glutaric anhydride succinic anhydride and the like.

Derivatives of such organic acid anhydrides may also be used. Thus, lower alkyl derivatives, for example methyl maleic anhydride, methyl glutaric anhydride, methyl succinic anhydride and halogen derivatives, for example tetrachlorophthalic anhydride and other suitable derivatives capable of reacting with the peroxygen compound to form a peroxy acid may be used. Either solid or liquid organic acid anhydrides can be used, but solid anhydrides are generally preferred.

While the bleaching composition of this embodiment may contain from about 0.75 to about parts by weight of the acid anhydride per part by weight of the peroxygen compound, generally it is preferred to use a 1:1 molar ratio of the acid anhydride and the peroxygen compound in the composition. Thus, the acid anhydride may comprise between about and 60% by weight of the second component of the two-component bleaching composition, with amounts between about and by weight being preferred.

The organic acid anhydride may be bonded to the expanded, porous inorganic carrier by several methods. According to one method, a solid acid anhydride is converted to a liquid state and contacted with the expanded, porous carrier particles whereby the acid anhydride is bonded to the particles. Thus, the solid acid anhydride may be heated to a temperature above its melting point to liquify the material and the liquified material applied to the porous, expanded particles in any suitable manner which provides intimate contact of the liquified material and the particles, such as by spraying, pouring, atomizing and the like. According to another method, a solid acid anhydride is first intimately mixed with the expanded, porous carrier particles and the mixture heated to a temperature above the melting point of the solid organic acid anhydride to thereby liquify the anhydride. As the anhydride melts, it is absorbed on the highly porous expanded salt particles to bond the anhydride thereto. When this technique is used, it is preferred that a lower hydrate of the expanded, porous carrier be used so that when the mixture is heated to melt the anhydride, water of hydration is not released.

Solid acid anhydrides may also be bonded to the expanded, porous carrier particles by first dissolving the anhydride in a suitable inert, volatile non-aqueous solvent and then applying the solvent solution to the carrier particles such as by spraying, pouring, atomizing or the like. The solution is readily absorbed by the porous salt particlles. The particles are continuously agitated during addition of the anhydride solution to provide a substantially uniform distribution of the anhydride throughout the mass of carrier particles. The inert solvent is then volatilized, leaving the acid anhydride deposited on and bonded to the porous particles. The solvent must, of course, be substantially anhydrous so that substantially no hydrolysis of the anhydride occurs. Suitable solvents include anhydrous ketones, anhydrous ethers, halogenated hydrocarbons and the like.

Acid anhydrides which are liquids may be bonded to the expanded porous salt particles by direct addition thereto such as by spraying, pouring, atomizing, or the like.

The expanded, porous carrier used in this second component of the bleaching composition is the same as that used as the carrier of the first component. Preferably, the expanded porous particles used in both components have substantially the same bulk density, that is between about 10 to 40 lbs./ cu. ft. and preferably between about 15 to 30 lbs/cu. ft., so that the physical mixture of the two components is substantially free from segregation, even after handling and storage.

The bleaching composition of this embodiment of the invention is prepared by dry mixing the two components in any suitable manner to provide a substantially uniform mixture of the two components. Generally, it is preferred to mix substantially equal amounts by weight of the two components. However, other ratios of the components may be admixed to provide a bleaching composition containing about 5% to 40% by weight of the peroxygen compound, about 5% to 40% by weight of the acid anhydride and about 0.1% to 5% by Weight of the alkali metal silicate, with the expanded porous carrier particles comprising substantially the remainder of the bleaching composition. Preferably the bleaching composition contains about 15% to 30% by weight of the peroxygen compound, about 15 to 30% by weight of the acid anhydride and about 0.5% to 3 by weight of the alkali metal silicate, balance carrier particles.

If desired, other materials may also be included in the bleaching composition provided they do not promote reaction or decomposition of the peroxygen or anhydride constituents during formation or storage. Thus, optical or fluorescent brightner materials, coloring agents, perfumes and the like may be bonded to the carrier particles.

In addition, the bleaching compositions of this invention may, if desired, be admixed with conventional organic surface active agents having detergent properties to provide a detergent composition having bleaching properties.

ll. Since the bulk density of the bleaching compositions may be readily controlled by controlling the bulk density of the carriers, the density of the bleaching composition may be matched to that of the detergent to prevent segregation of the bleaching and the detergent components upon handling, shipping and storage.

The following examples are set forth to illustrate, not to limit, the invention whereby those skilled in the art may understand more fully the nature in which the present invention can be carried into effect. In the instant specification and appended claims, all parts and percentages are by weight unless otherwise indicated.

Example 1.A dry, stable peroxygen bleaching composition having a relatively low bulk density is prepared in the following manner.

A quantity of sodium tetraborate pentahydrate is expanded according to the procedure disclosed in said copending patent application Ser. No. 387,137, now Pat. No. 3,454,357 to provide a quantity of expanded, porous particles which are then dried to reduce the water of hydration content thereof to about 1.2 mole of water per mole of tetraborate. The dried particles thus produced have a bulk density of about 19.1 lbs/cu. ft.

A measured quantity of the dried expanded, porous sodium tetraborate particles and an equivalent amount by weight of particulate sodium perborate tetrahydrate, having a bulk density of about 43 lbs./ cu. ft., are introduced into a container in a controlled temperature oven. The expanded sodium tetraborate and the sodium perborate are heated, while continuously agitated, to a temperature of between about 65 -70 C. for about ten minutes. At this temperature water of hydration is released from the perborate and the released water is rapidly taken up by the dried tetraborate particles to bond the perborate to the particles and provide a uniform, free-flowing, nonsegregating product. Agitation of the product is continued while the product cools. Since the perborate is bonded to the expanded porous tetraborate particles, separation of these two constituents is substantially prevented during handling and storage.

A decomposition inhibitor, sodium metasilicate, is included in the composition by mixing about 22 grams of finely divided metasilicate with about 886 grams of the bonded sodium perborate-sodium tetraborate product. The metasilicate in the resulting composition is not bonded to the tetraborate particles in the resulting composition but is physically mixed therewith.

The bulk density of the resulting composition is 24 lbs./ cu. ft. The available oxygen content of the bleaching composition thus prepared is determined after formulation and after fourteen weeks storage. There is substantially no loss in available oxygen content after this prolonged period of storage, thereby demonstrating the storage stability of the composition.

The bleaching composition prepared in the manner described above is subjected to a series of test to compare the bleach activity of the composition of this invention with that of an equivalent amount of fresh sodium perborate. In this series of tests a standard procedure is followed in which test cloths were washed in an agitatortype washer under standard conditions of temperature, agitation rate and wash water. Tests are made using cloths stained with tea, ink, vacuum cleaner dust and chlorophyll.

The following test procedure is used: the percent reflectancc of each test cloth is first determined. The test cloth is then washed for minutes in wash water containing 0.70 gram sodium perborate per liter at a tem- "erature of 194 F. Following the wash cycle the cloth is subjected to two 3-minute rinse cycles, after which it is dried, ironed and the percent reflectance again measured. The change in percent reflectance is determined for each test cloth and the results set out below in Table 1.

The results of this series of tests clearly show that the composition of this invention is as effective a bleach as perborate alone. However, the present bleaching composition is superior to conventional peroxygen bleaches for the present composition has excellent storage stability and has a controllable, moderately low bulk density. In addition, the sodium perborate, which is bonded to the expanded, porous carrier, does not separate or segregate from the composition so its concentration remains substantially uniform throughout the composition.

Example 2.-Fifty grams of dried expanded, porous sodium tetraborate, containing about one mole of water of hydration and grams of sodium perborate tetrahydrate are placed in a rotating flask and heated to C. for about 10 minutes at which time the temperature is raised to about C. for an additional 5 minutes. The contents of the flask are then allowed to cool while rotation is continued. The water of hydration released from the sodium perborate upon heating is distributed among the constituents of the mixture and is rapidly taken up by the expanded porous tetraborate particles thereby bonding the perborate to the particles. A dry, free-flowing bonded product is thereby produced. On analysis, the bonded composition is found to contain 5.2% available oxygen. After storage for 16 weeks the composition still contains 5.2% available oxygen, thus demonstrating the remarkable stability of this product.

Example 3.-This example illustrates the manner in which a peroxygen bleaching composition may be prepared according to the present invention, without heating, by applying a controlled amount of moisture to the constituents. As discussed hereinabove, the water present in the system may be no more than that required to completely hydrate the materials used.

Six hundred twenty-five grams of expanded, porous sodium tetraborate (containing 21.2% H 0) and 625 grams of finely divided sodium perborate tetrahydrate are placed in a container which is then rotated at an angle so that the solids tumble and roll as the container is rotated. A solution of 32.7 grams of sodium metasilicate in 79 grams of water is then slowly sprayed onto the moving particles bonding the constituents of the mixture together. Rotation of the particles was continued to provide a dry, free-flowing composition in which the perborate and metasilicate constituents are bonded to the expanded, porous tetrahydrate particles.

A portion of this bonded composition is placed in a jar and vibrated for one hour. Samples taken from the top and bottom of the jar at the end of the one-hour period contain 4.20 and 4.24% available oxygen, respectively. This clearly shows the eifectiveness of the present invention in bonding the perborate and metasilicate constituents to the expanded porous carrier so that separation of these constituents from the composition will not occur during handling, shipping, storage or the like.

Example 4.Fifty grams of finely divided sodium perborate tetrahydrate, 49.5 grams of dried expanded, porous sodium tetraborate particles and 0.5 gram finely divided sodium metasilicate pentahydrate are placed in a rotating flask and heated to about C. The materials are maintained at this temperature for about 5 minutes with rotation. The contents of the flask are then permitted to cool to room temperature while rotation of the flask is continued. The water of hydration released upon heating is 13 redistributed among the constituents of the mixture and effectively bonds the perborate and metasilicate constituents to the expanded, porous tetraborate particles. The bonded product has a bulk density of 21.8 lbs/cu. ft. and an available oxygen content of about 5.3%.

Substantially similar results are obtained when the expanded porous sodium tetraborate carrier of this example is replaced by expanded, porous particles of potassium tetraborate, sodium carbonate, sodium sulfate, tetrasodium pyrophosphate and sodium metaborate, respectively. While the bulk density of the bleaching composition is usually somewhat higher when inorganic salts other than sodium tetraborate are used as the carrier, it is still within the desired limits.

Repetition of this example using a peroxygen compound other than sodium perborate, such as alkali metal and alkaline earth metal peroxides, percarbonates, persulfates and perphosphates, provides a dry, stable, non-segregating bleaching composition in which the peroxygen compound is bonded to the expanded, porous carrier.

Similarly, repetition of this example using a decomposition inhibitor other than sodium metasilicate such as sodium orthosilicate, sodium sesquisilicate, magnesium silicate, barium silicate, calcium silicate and conventional metal chelating agents such as ethylene diamine tetraacetic acid provides a stable, non-segregating bleaching composition in which the decomposition inhibitor is bonded with the peroxygen compound to the expanded porous carrier.

The procedure described hereinabove in Examples 1-4 provides a dry, free-flowing bleaching composition which is as effective a bleach as perborate alone at the relatively high temperatures at which such peroxygen bleaches are usually used. The bleaching composition of these examples is, however, far superior to conventional perborate bleaches for the present composition has excellent storage stability, a controllable, moderately low bulk density and is not subject to separation or segregation of the constituents during handling, shipping or storage.

The following examples are illustrative of the preparation of the two-component bleaching composition described hereinabove which is not onl stable, non-segregating and has a controllable, moderately low bulk density but is also an effective bleach at mild temperatures.

Example 5.-The first component of the two-component bleaching composition, which comprises a quantity of expanded, porous carrier particles having a peroxygen compound and an alkali metal silicate bonded thereto, is provided in the following manner.

A quantity of expanded, porous sodium tetraborate particles is dried by heating to about 200 C. to reduce the water of hydration content to about 1.2 mole of water per mole of tetrahydrate. Ninety-six grams of the dried tetraborate particles are introduced into a rotating flask followed by the addition of 4 grams of solid anhydrous sodium metasilicate and 100 grams of finely divided sodium perborate tetrahydrate. The mixture in the rotating flask is heated to about 65 C. and this temperature malntained for about minutes while rotation is continued. The flask and its contents are then permitted to cool to room temperature with continued rotation of the flask. The water of hydration released by the sodium perborate tetrahydrate upon heating is redistributed among the in gredients in the mixture and taken up by the expanded porous particles to effectively bond the sodium perborate and the sodium metasilicate to the particles and provide a dry, free-flowing composition. Since the sodium perborate and sodium metasilicate are bonded to the expanded, porous sodium tetraborate particles, separation of these constituents in the composition is prevented. The composition thus produced contains about 5.30% available oxygen and has a bulk density of about 23 lbs./cu. ft. This composition is the first component of the twocomponent, low-temperature bleaching composition.

The second component of the bleaching composition is prepared by admixing 125 grams of dried expanded,

porous sodium tetraborate particles and grams of phthalic anhydride in a rotating flask while heating the rotating flask and its contents to about C. for about 20 minutes. The phthalic anhydride is molten at this temperature and is absorbed on the highly porous sodium tetraborate particles. The flask and its contents are then cooled to room temperature with continued rotation. The resulting product is a dry, free-flowing material in which the phthalic anhydride is bonded to the expanded porous sodium tetraborate particles. This product has a bulk density of about 21.2 lbs/cu. ft.

This second component is tested for separation of the constituents by vibrating a sample of the bonded product for one hour in a jar and then taking a one-gram sample from the top and the bottom of the jar. Both samples are tested by adding 0.5 gram sodium perborate to each sample, dissolving the samples in Water and measuring the amount of available oxygen in the perphthalic acid formed in each sample. The top sample produced 3.1% available oxygen as perphthalic acid and the bottom sample 3.0% available oxygen as perphthalic acid, thereby demonstrating that the acid anhydride is effectively bonded to the expanded porous carrier and does not separate therefrom.

The fully compounded, two-component, low-temperature bleach is prepared by dry mixing approximately equal amounts by weight of the first and second components prepared above. This final bleach composition, which is dry and free-flowing, contains 2.1% total available oxygen immediately after preparation. Reanalysis 14 days later shows no decomposition, thereby demonstrating the excellent storage stability of the composition. Since both composition have approximately the same bulk density, segregation of the component does not occur on handling, shipping, storage or the like.

Example 6.A two-component, low-temperature bleaching composition is prepared in the following manner. A measured quantity of dried, expanded, porous sodium tetraborate particles having a bulk density of 19 lbs./cu. ft. is introduced into a flask together with an equivalent amount by weight of sodium perborate tetrahydrate, having a bulk density of about 43 lbs./ cu. ft. The flask is rotated to admix the tetraborate and perborate constituents and the mixture in the flask is first heated to about 55 C. for 10 minutes and then to about 70 C. for an additional 10 minutes. At this temperature the mixture is slightly moist due to the release of water of hydration from the sodium perborate, which is substantially uniformly distributed throughout the mixture. The mixture is then allowed to cool to room temperature while rotation of the flask is continued. The resulting product is a dry, free-flowing composition of sodium perborate bonded to the expanded sodium tetraborate particles.

Sodium metasilicate is then included in the composition by mixing about 22 grams of finely divided sodium metasilicate with about 886 grams of the bonded sodium perboratesodium tetraborate product. The metasilicate in the resulting composition is not thereby bonded to the tetraborate particles but is uniformly distributed throughout the composition as a physical mixture.

While such a mere physical mixture of the metasilicate in the composition is generally not preferred, it is still effective in providing a bleaching composition which may be used at mild temperatures. This first component of the bleaching composition formed in this manner has a bulk density of 24 lbs/cu. ft., an available oxygen content of 4.8%, and has the composition Percent Sodium tetraborate 48.8 Sodium perborate 48.8 Sodium metasilicate 2.4

Reanalysis after 14 weeks storage shows no loss in available oxygen content, thereby demonstrating the excellent storage stability of this component of the composition.

The second component of the two-component bleaching composition is prepared by admixing 200 grams of the dried expanded sodium tetraborate particles and 200 grams of particulate phthalic anhydride in a rotating flask. The mixture is heated to about 135 C. to thereby melt the solid phthalic anhydride with the molten anhydride being rapidly absorbed by the porous sodium tetraborate particles. The mixture is then cooled to room temperature with continued rotation. The resulting composition comprises phthalic anhydride bonded to the expanded sodium tetraborate particles and has a bulk density of 24 lbs/cu. ft.

The two-component, low-temperature bleaching composition of this invention is prepared by admixing 400 grams of the first component (containing 48.8% sodium tetraborate, 48.8% sodium perborate and 2.4% sodium metasilicate) and 400 grams of the phthalic anhydridesodium tetraborate second component. An additional grams of finely divided sodium metasilicate is physically mixed with and uniformly distributed throughout the mixture of these two compounds. The resulting composition has a bulk density of 26 lbs./ cu. ft., an available oxygen content of 2.5% and has the composition Percent Sodium tetraborate 48.8 Sodium perborate 24.1 Phthalic anhydride 24.7 Sodium metasilicate 2.4

Analysis of the composition for available oxygen content 12 weeks after preparation shows 2.1% thereby demonstrating the stability of the composition. Since the bulk density of the first and second components are substantially the same, segregation of these components in the composition is substantially eliminated.

The bleaching composition prepared in this manner is then subjected to a series of tests to compare the bleach activity of this composition with that of sodium perborate at 50 C. The procedure followed in this series of tests is the same as that described in Example 1 with the single exception that the bleaching composition was evaluated in this example at 50 C. instead of 90 C. The results of this test, expressed in change in percent reflectance of the stained cloths used in the test, are set forth in Table II.

TABLE II Change in percent reflectance Two-cornponent bleaching The results of this series of tests clearly shows the effectiveness of this two-component bleaching composition of this invention at moderately low temperatures. Not only is this composition an etfective bleach at mild temperatures, but it provides a number of other advantages over peroxygen bleaches presently available, for it is dry, free-flowing, has excellent shelf stability, has a controllable, moderately-low 'bulk density and is free from segregation.

Example 7.As discussed hereinabove the acid anhydride constituent of the second component of the lowtemperature bleaching composition may be bonded to the expanded, porous particles by dissolving the solid anhydride in a volatile, non-aqueous solvent and applying the resulting solution to the expanded porous particles. Thus, the second component of the bleaching composition may be prepared in the following manner.

Two hundred twenty grams of solid phthalic anhydride are dissolved in 1200 ml. of reagent grade acetone. This solution is sprayed onto 220 grams of expanded porous sodium tetraborate particles (having a water content of about 21.2%) with agitation of the particles. The tetraborate particles are continuously agitated while the acetone is allowed to evaporate. Upon completion of the evaporation of the acetone, a dry, free-flowing product is provided, the product comprising phthalic anhydride deposited on and bonded to the expanded lporous sodium tetraborate particles.

This second component of the composition is mixed with an equal weight of the first component to provide the two-component bleaching composition of this embodiment. This first component is prepared by bonding sodium per-borate tetrahydrate to undried expanded, porous sodium tetraborate particles (containing 21.2% water) at room temperature *by spraying onto a mixture of these constituents an aqueous solution of sodium metasilicate, according to the procedure described in Example 3.

While this preferred embodiment has been particularly described with reference to the use of sodium perborate as the peroxygen compound, sodium metasilicate as the alkali metal silicate, phthalic anhydride as the organic acid anhydride and expanded, porous sodium tetraborate particles as the expanded, porous inorganic carrier, it will be understood that other compounds may also be used. Thus, in the preferred two-component bleaching composition of this invention, any of the peroxygen compounds, alkali metal silicates, acid anhydrides and expanded porous inorganic carriers described hereinabove may also be used.

In accordance with another aspect of this invention, there is provided a composition having oxidizing and bleaching properties which comprises a substantially uniform mixture of a first quantity of expanded, porous inorganic salt particles having at least one water-soluble inorganic peroxygen compound bonded thereto and a second quantity of said expanded porous inorganic salt particles having bonded thereto at least one organic acid anhydride. This combination of ingredients provides a dry, free-flowing bleaching composition of controllable, moderately low bulk density. When this composition is added to water or aqueous liquids, the peroxygen compound and acid anhydride react to form a peroxyacid of the acid anhydride which is an active and efiective oxidizing and bleaching agent. Since the peroxygen compound and the acid anhydride are bonded to separate quantities of the expanded porous particles, premature reaction between these compounds, which may occur should there be any free water present during handling and storage of the composition, is prevented. Also, the expanded porous particles to which the peroxygen compound and the acid anhydride are bonded are able to absorb a substantial amount of atmospheric moisture and bind it tightly as water of hydration to thereby prevent decomposition or reaction of these materials prior to use.

'Peroxygen compounds which may be used in this embodiment of the invention include, for example, alkali metal and alkaline earth metal perborates, peroxides, percarbonates, persulfates, perphosphates and the like, either singly or in combination. These peroxygen compounds may be either anhydrous or in a hydrated state. At least one of said peroxygen compounds is bonded to a first quantity of the expanded, porous inorganic salt particles in the manner described hereinabove for bonding a peroxygen compound to expanded particles, namely by intimately mixing the peroxygen compound and the expanded, porous particles at moderately low temperatures under relatively dry conditions. Thus, the amount of water present in said mixture is maintained at a value less than the amount which can be completely bound as the highest hydrate of the peroxygen compound and the expanded, porous salt particles.

A wide variety of organic acid anhydrides may be used in this embodiment of the invention. Generally, any organic acid anhydride which reacts with the peroxygen compound when added to water to form a peroxyacid may be used. Suitable organic acid anhydrides which may be used include, for example, acetic anhydride, priopionic anhydride, n-butyric anhydride, iso-butyric anhydride, valeric anhydride, phthalic anhydride, glutaric anhydride, succinic anhydride, maleic anhydride and the like, either singly or in combination. At least one of said organic acid anhydrides in bonded to a second quantity of said expanded, porous particles according to the procedure described hereinabove for bonding such materials.

Any one of the expanded, porous inorganic salts disclosed hereinabove may be used in this embodiment of the invention. Both the first quantity of expanded, porous particles (to which the peroxygen compound is bonded) and the second quantity of said particles (to which the acid anhydride is bonded) have a bulk density of between about to 40 lbs./cu. ft. and preferably between about to 30 lb./cu. ft., so that the mixture of the two ouantities is substantially free from segregation.

The bleaching composition of this embodiment is prepared by mixing the two quantities of expanded porous particles, having the peroxygen compound and acid anhydride bonded thereto, in any suitable manner to provide a substantially uniform mixture. Generally, it is preferred to provide a composition containing substantially equirnolar amounts of the peroxygen compound and the acid anhydride. However, other ratios of peroxygen compound to acid anhydride may be used in the bleaching composition as long as there is a sufiicient amount of each reactant in the composition to provide an effective oxidizing and bleaching agent.

If desired, at least one peroxygen decomposition inhibitor may also be included in this composition. Preferably, such a decomposition inhibitor is bonded to the first quantity of expanded porous particles to which the peroxygen compound is bonded. Suitable decomposition inhibitors which may be used include, for example, alkali metal and alkaline earth metal silicates, metal chelating agents and the like. The decomposition inhibitor may comprise between about 0.1% and 6% by weight of the bleaching composition.

In summary, the present invention provides a dry, stable, non-segregating bleaching composition of controllable, moderately low bulk density. Thus, the constituents in the composition do not decompose, hydrolyze or interact on storage and do not separate or segregate on handling or storage. Since the bulk density of the bleaching composition can be controlled by controlling the bulk density of the expanded, porous carrier particles, the bleaching composition can be mixed with detergents or other additives without segregation of the materials in such compositions. In addition, the two-component bleaching composition of this invention provides a bleach which is effective even at mild temperatures. Since the peroxygen and silicate constituents are bonded to one quantity of expanded, porous particles and the acid anhydride constituent is bonded to a separate quantity of the expanded porous carrier particles, interaction between these constituents is effectively prevented during storage and/or handling so that the composition has excellent storage stability. However, upon addition of the composition to an aqueous medium the constituents react rapidly to provide oxidative species having a high oxidative potential and thereby provide an excellent oxidative bleach.

Although the present invention has been described and illustrated with reference to specific examples, it will be understood that changes, modifications and variations of composition and procedure may be made by those skilled in the art within the principle and scope of the inventions set forth in the appended claims.

What is claimed is:

1. A dry, stable, free-flowing bleaching composition consisting essentially of a quantity of expanded, porous, water-soluble inorganic hydrate salt particles having between about 10% and 60% by weight of at least one water-soluble inorganic peroxygen compound which is capable of forming hydrogen peroxide in an aqueous solution bonded thereto said expanded, porous salt particles having a bulk density of from about 10 to 40 lbs/cu. ft. and being selected from the group consisting of hydrates of alkali metal borates, carbonates, sulfates and phosphates.

2. The composition defined in claim 1 in which said peroxygen compound is selected from the group consisting of hydrated and anhydrous alkali metal and alkaline earth metal perborates, peroxides, percarbonates, persulfates and perphosphates.

3. The composition defined in claim 1 in which said inorganic salt is sodium tetraborate and said peroxygen compound is sodium perborate.

4. The composition defined in claim 1 in which a peroxygen decomposition inhibitor selected from the group consisting of alkali metal silicates, alkaline earth metal silicates and ethylene tetracetic acid is bonded to said expanded porous salt particles in an amount to provide between about 0.1% and 6% by weight of said decomposition inhibitor.

5. A method of preparing a dry, free-flowing, stable bleaching composition which comprises admixing between about 10% and 60% by weight of at least one water-soluble inorganic peroxygen compound which is capable of forming hydrogen peroxide in an aqueous solution with a quantity of expanded, porous water-soluble inorganic salt particles selected from the group consisting of alkali metal borates, carbonates, sulfates and phosphates, said expanded salt particles having a bulk density of from about 10 to 40 lbs/cu. ft. under relatively dry conditions in the presence of a controlled amount of water which can exchange between said materials, whereby said Water is rapidly taken up by said expanded, porous particles and bonds said peroxygen compound thereto to provide a dry, stable free-flowing composition.

6. The method defined in claim 5 in which said water is provided in said admixture by adding water at a controlled rate to said admixture of the peroxygen compound and said expanded, porous inorganic salt particles while said admixture is agitated.

7. The method defined in claim 5 in which at least one of said peroxygen compound and said inorganic salt is present in said admixture as a hydrate which is capable of releasing water of hydration upon heating, and said water is provided in said admixture by heating, while agitating, the admixture to at least the temperature at which one of the hydrates in said admixture releases at least a portion of its water of hydration.

8. The method defined in claim 5 in which said peroxygen compound comprises sodium perborate tetrahydrate and said expanded, porous inorganic salt comprises particles of expanded sodium tetraborate having a water of hydration content of about 1 to 2 moles of water per mole of said tetraborate, and said admixture is heated, with agitation, to a temperature of between about 60 to C. for a period of time suflicient to release water of hydration from said sodium perborate.

9. The method defined in claim 5 in which said peroxygen compound is selected from the group consisting of alkali metal and alkaline earth metal perborates, peroxides, percarbonates, persulfates and perphosphates.

10. The method defined in claim 5 in which said peroxygen compound is admixed with said expanded porous salt particles in the presence of at least one peroxygen decomposition inhibitor under relatively dry conditions in the presence of a controlled amount of water whereby said peroxygen compound and said decomposition inhibitor are bonded to said expanded, porous salt particles, said decomposition inhibitor being selected from the group consisting of alkali metal silicates, alkaline earth metal silicates and ethylene tetracetic acid, and said decomposition inhibitor being present in said admixture in an 19 amount sufficient to provide a composition containing between about 0.1% and 6% by Weight of said inhibitor.

11. The method defined in claim 10 in which at least one of said peroxygen compound, said peroxygen decomposition inhibitor and said inorganic salt is present in said admixture as a hydrate which is capable of releasing water of hydration upon heating, and said water is provided in said admixture by heating the admixture, while agitating, to at least the transition temperature of the hydrate in said admixture to thereby release said water.

12. The method defined in claim 10 in which said water is provided in said admixture by adding moisture at a control rate to said admixture of said peroxygen compound, said peroxygen decomposition inhibitor and said expanded, porous inorganic salt particles.

13. The method defined in claim 10 in which an aqueous solution of said decomposition inhibitor is applied to an admixture of said peroxygen compound and said expanded, porous salt particles whereby the water present in said aqueous solution is rapidly taken up by said expanded porous particles to bond said peroxygen compound and said peroxygen decomposition inhibitor to said expanded, porous particles.

14. A dry, free-flowing bleaching composition consisting essentially of a substantially uniform mixture of a first quantity of expanded, porous water-soluble inorganic hydrate salt particles having between about to 40% by weight of at least one water-soluble inorganic peroxygen compound which is capable of forming hydrogen peroxide in an aqueous solution bonded thereto and a second quantity of said expanded, porous water-soluble inorganic hydrate salt particles having bonded thereto between about 5% to 40% by weight of at least one organic acid anhydride selected from the group consisting of acetic anhydride, propionic anhydride, n-butyric anhydride, iso-butyric anhydride, valeric anhydride, phthalic anhydride, glutaric anhydride, succinic anhydride, maleic anhydride and halogen and lower alkyl derivatives thereof which are capable of reacting with said peroxygen compound in an aqueous medium to form a peroxy acid of said acid anhydride, said inorganic hydrate salt being selected from the group consisting of hydrates of alkali metal borates, carbonates, sulfates and phosphates having a bulk density of from about to 40 lbs/cu. ft.

15. The composition defined in claim 14 in which said peroxygen compound is selected from the group consisting of alkali metal and alkaline earth metal perborates, peroxides, percarbonates, persulfates and perphosphates.

16. The composition defined in claim 14 in which the composition contains substantially equimolar amounts of said peroxygen compound and said acid anhydride.

17. The composition defined in claim 14 in which at least one peroxygen decomposition inhibitor selected from the group consisting of alkali metal silicates, alkaline earth metal silicates and ethylene tetracetic acid is bonded to said first quantity of expanded porous particles, said decomposition inhibitor comprising between about 0.1 and 6% by weight of the composition.

18. The composition defined in claim 14 in which said first quantity of expanded porous particles has bonded thereto at least one water-soluble peroxygen compound which is capable of forming hydrogen peroxide in an aqueous medium and at least one water-soluble alkali metal silicate, and said second quantity of expanded porous particles has bonded thereto at least one organic acid anhydride which is capable of reacting with said peroxygen compound in an aqueous medium to form a peroxy acid of said acid anhydride.

19. The composition defined in claim 18 in which said composition contains about to by weight of said peroxygen compound, about 15% to 30% by weight of said acid anhydride and about 0.5% to 3% by weight of said alkali metal silicate, with said expanded, porous, inorganic hydrate salt particles comprising substantially the remainder Of Said bleaching composition.

20. The composition defined in claim 18 in which said peroxygen compound is selected from the group consisting of alkali metal and alkaline earth metal peroxides; alkali metal and alkaline earth metal perborates; salts of peroxyacids; and peroxyhydrates.

21. The composition defined in claim 18 in which said alkali metal silicate is selected from the group consisting of sodium metasilicate, sodium orthosilicate, sodium sesquisilicate, sodium disilicate, potassium metasilicate and potassium disilicate.

22. The composition defined in claim 18 in which said first quantity of expanded porous particles comprises a mass of expanded, porous sodium tetra borate particles having sodium perborate and sodium metasilicate bonded thereto and said second quantity of expanded porous particles comprises a mass of expanded porous sodium tetraborate particles having phthalic anhydride bonded thereto, said expanded, porous sodium tetraborate particles in both of said first and second quantity having substantially the same bulk density within the range of from about 15 to 30 lbs/cu. ft.

23. A method of preparing a dry, free-flowing bleaching composition comprising a substantially uniform mixture of a first component and a second component, said method comprising:

preparing said first component by contacting between about 5% and 40% by weight of at least one watersoluble inorganic peroxygen compound which is capable of forming hydrogen peroxide in an aqueous solution with a first quantity of expanded, porous water-soluble inorganic hydrate salt particles selected from the group consisting of hydrates of alkali metal borates, carbonates, sulfates and phosphates under relatively dry conditions in the presence of a controlled amount of water, the amount of water present in said admixture being maintained at a value less than the amount which can be completely bound as the highest hydrate of said peroxygen compound and said inorganic hydrate salt, whereby said water present in said admixture is rapidly taken up by said expanded, porous particles to bond said peroxygen compound thereto,

preparing said second component by contacting a second quantity of said expanded, porous Water-soluble inorganic hydrate salt particles with between about 5% and 40% by weight of at least one organic acid anhydride, which is in a liquid state, selected from the group consisting of acetic anhydride, propionic anhydride, n-butyric anhydride, iso-butyric anhydride, valeric anhydride, phthalic anhydride, glutaric anhydride, succinic anhydride, maleic anhydride and halogen and lower alkyl derivatives thereof which are capable of reacting with said peroxygen compound in an aqueous medium to form a peroxy acid of said acid anhydride whereby the anhydride is bonded to said expanded, porous particles, and

intimately mixing said first and said second components to provide a substantially uniform mixture of said components.

24. The method defined in claim 23 in which said first component is prepared by contacting said peroxygen compound with said expanded porous particles in the presence of at least one peroxygen decomposition inhibitor under relatively dry conditions in the presence of a controlled amount of water whereby said peroxygen compound and said decomposition inhibitor are bonded to said expanded, porous particles.

25. The method defined in claim 24 in which said first component is prepared by contacting at least one watersoluble peroxygen compound which is capable of forming hydrogen peroxide in an aqueous medium and at least one water-soluble alkali metal silicate with said first quantity of expanded, porous particles and said second component is prepared by contacting said second quantity of expanded porous particles with at least one organic acid anhydride which is capable of reacting with said peroxygen compound in an aqueous medium to form a peroxy acid of said acid anhydride.

26. The method defined in claim in which said peroxygen compound is selected from the group consisting of alkali metal and alkaline earth metal peroxides; alkali metal and alkaline earth metal perborates; salts of peroxyacids; and peroxyhydrates.

27. The method defined in claim 25 in which said alkali metal silicate is selected from the group consisting of sodium metasilicate, sodium orthosilicate, sodium sesquisilicate, sodium disilicate, potassium metasilicate and potassium disilicate.

28. The method defined in claim 25 in which said first component is prepared by adding water at a controlled rate to said admixture of said peroxygen compound, said alkali metal silicate and said expanded porous particles to bond said peroxygen compound and said silicate to said expanded porous particles.

29. The method defined in claim 25 in which said first component is prepared by adding an aqueous solution of said alkali metal silicate to an admixture of said peroxygen compound and said expanded, porous particles whereby the Water present in said aqueous solution is rapidly taken up by said expanded, porous particles to bond said peroxygen compound and said alkali metal silicate thereto.

30. The method defined in claim 25 in which said first component is prepared by admixing said peroxygen compound, said alkali metal silicate and said expanded, porous inorganic salt, at least one of which is present in said admixture as a hydrate which is capable of releasing water upon heating and heating the admixture to the temperature at which water of hydration is released from said hydrate in said admixture, with said released water being absorbed by said expanded porous particles to thereby bond said silicate and said peroxygen compound thereto.

31. The method defined in claim 25 in which said first component is prepared by admixing higher hydrates of said peroxygen compound and said alkali metal silicate with expanded, porous particles of a lower hydrate of said inorganic salt and heating said admixture to at least the temperature at which water of hydration is released from one of said higher hydrates whereby said released water is taken up by said expanded, porous particles to thereby bond said peroxygen compound and said alkali metal silicate to said expanded, porous particles.

32. The method defined in claim 25 in which said second component is prepared by admixing a solid organic acid anhydride and said expanded, porous particles and heating the mixture to a temperature above the melting point of said acid anhydride to liquify the acid anhydride, said liquified acid anhydride being absorbed on the expanded, porous salt particles and bonded thereto.

33. The method defined in claim 25 in which said second component is prepared by dissolving said acid anhydride in a nonaqueous, volatile inert solvent to form a solution of said anhydride in said solvent, applying said solution to said expanded, porous salt particles and volatilizing off said solvent to thereby bond said acid anhydride to said expanded porous particles.

34. The method defined in claim 25 in which said first component is prepared by admixing sodium perborate tetrahydrate and sodium metasilicate with a mass of expanded porous sodium tetraborate particles having a water of hydration content of about 1 to 2 moles of water per mole of said tetraborate and heating said admixture with agitation to a temperature of between about and C. for a period of time suflicient to release water of hydration from said hydrated sodium perborate whereby said released water of hydration is rapidly taken up by said expanded, porous tetraborate particles to bond said perborate and said metasilicate thereto, said second component is prepared by admixing solid phthalic anhydride with a mass of expanded porous sodium tetraborate particles and heating said admixture to a temperature of at least about C. to liquify said phthalic anhydride whereby said liquified phthalic anhydride is absorbed on and bonded to said tetraborate particles, and said first and second components are dry mixed to provide a substantially uniform mixture of said components.

References Cited UNITED STATES PATENTS 2,838,459 6/1958 Sprout 252186 3,140,149 7/ 1964 Habernickel 252186 3,298,775 1/1967 Malafosse et al. 252186 RICHARD D. LOVERING, Primary Examiner I. GLUCK, Assistant Examiner US. Cl. X.R.

Patent No. 3,640,885 Dated February 8, 1972 lnventor(s) Raymond C. Rhees It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 6, Assignor should be Kerr-McGee Chemical Corp.

Column 4, line 18, formula should read -Na B O -lOH O-.

Column 8, line 14, "constiuens" should be --constituents-- "he" should be --the--. line 66, "perbonate" should be --perborate--.

Column 17, line 6, "in" should be --is--.

Signed and sealed this 20th day of June 1972.

{SE.AL)

Attest:

EDWARD MELETCHER, JRa ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PO-IOSO (10-69) USCOMM DC 603764369 us. GOVERNMENT PRINTING OFFICE: I959 O366334 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 7 Patent No. 3,640,885 Dated February 8, 1972 Inventor(s) Raymond C. Rhees It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 6, Assignor should be Kerr-McGee Chemical Corp.

Column 4, line 18, formula should read --Na B O-,'1OH O--.

Column 8, line 14, "constiuens" should be --constituents-- "he" should be --the--. line 66, "perbonate" should be --perborate- Column 17, line 6, "in" should be --is---.

Signed and sealed this 20th day of June 1972.

ISEAL) Attest:

EDWARD M.FLETCHER, JR. ROBERT GOTTSCHALK Att'esting Officer Commissioner of Patents FORM PC4050 (10459) USCOMM-DC 60376-P69 I l-LSv GOVERNMENT PRlNTlNG OFFICE t 959 0-356-334 

